The present invention relates generally to methods and systems for performing in-vivo flow cytometry, and more particularly, to methods and systems for performing non-invasive in-vivo flow cytometry.
Conventional flow cytometric techniques known in the art for detecting and/or quantifying desired cell types flowing through a subject's circulatory system typically require extraction of blood from the subject followed by labeling and ex-vivo detection. For example, in standard ex-vivo flow cytometry, cells present in a blood sample, drawn from a subject, are fluorescently labeled, and passed in a single file through a flow stream to be interrogated by a light source so as to derive cytometric information. In another ex-vivo conventional technique, known as hemocytometry, cells are counted against a grid while being viewed with a microscope to determine cell types and numbers.
Such ex-vivo techniques, however, suffer from a number of shortcomings. For example, each measurement provides only a single time sample. Consequently, it is difficult to use these techniques to obtain a reliable temporal cell population profile for a cell type of interest that varies unpredictably or rapidly with time. Further, such conventional techniques can suffer from a significant time delay between sample collection and analysis, which can potentially lead to measurement inaccuracies.
Some in-vivo techniques for detection of static and circulating fluorescently-labeled cells are also known. Many of these techniques, however, show difficulty, or simply fail, in tracking cells flowing at a high velocity, especially in the arterial circulation, even when they capture images at video rates. In addition, in many of such techniques, extracting quantitative information from acquired data may be tedious. Moreover, in some cases, fluorescent probes for labeling a cell type of interest may not be available.
Hence, there is a need for enhanced methods and systems for performing in-vivo flow cytometry.